What is Chlamydia trachomatis?

Chlamydia Trachomatis: A Comprehensive Overview

Chlamydia trachomatis is the most common sexually transmitted bacterial pathogen globally, causing an estimated 3 million new infections annually in the United States alone, with significant potential for serious reproductive health complications including pelvic inflammatory disease, infertility, and ectopic pregnancy. 1

Microbiology and Characteristics

Chlamydia trachomatis is an obligate intracellular bacterial pathogen that:

• Infects squamocolumnar or transitional epithelial cells 2
• Has a unique developmental cycle requiring host cells for replication
• Cannot be grown on standard bacterial culture media
• Is classified as a gram-negative bacterium 3

Epidemiology

• Most prevalent in young adults aged 14-25 years 2
• 70-90% of infected women and a large percentage of men are asymptomatic 1
• Prevalence varies by population:
  • 4-12% among female family planning clinic patients
  • 9% among female Army recruits
  • 2-7% among female college students 1
• Areas with established screening programs have shown significant declines in prevalence 1

Clinical Manifestations

In Adults

1. Women:

   • Cervicitis (often asymptomatic)
   • Pelvic inflammatory disease (PID)
   • Reproductive sequelae: infertility, ectopic pregnancy, chronic pelvic pain 2, 4

2. Men:

   • Nongonococcal urethritis
   • Epididymitis
   • Potential complications: infertility, chronic prostatitis, reactive arthritis, urethral strictures 1

3. Both sexes:

   • Proctitis (rectal infection)
   • Reactive arthritis
   • Increased risk of acquiring HIV infection 1

In Neonates

• Conjunctivitis developing 5-12 days after birth (most common identifiable infectious cause of ophthalmia neonatorum) 1
• Subacute, afebrile pneumonia with onset at 1-3 months of age 1
• Characteristic signs of chlamydial pneumonia include:
  • Repetitive staccato cough with tachypnea
  • Hyperinflation and bilateral diffuse infiltrates on chest radiograph
  • Typically afebrile
  • Possible peripheral eosinophilia 1

Diagnostic Testing

Modern diagnostic methods include:

1. Nucleic Acid Amplification Tests (NAATs):

   • Highest sensitivity (82-100%) and specificity (96-100%) 1
   • Can be performed on various specimen types:
     • Endocervical/urethral swabs
     • Urine specimens (allowing non-invasive testing)
     • Self-collected vaginal swabs 1

2. Antigen Detection Tests:

   • Direct fluorescent antibody (DFA) assay
   • Enzyme immunoassay (EIA)
   • Slightly lower sensitivity (70-80%) but high specificity (96-100%) 1

3. Culture:

   • Historically considered the gold standard
   • Requires specialized handling and laboratory services
   • Still the definitive standard for chlamydial pneumonia 1

Treatment

For Adults with Uncomplicated Infection

Recommended Regimens:

• Azithromycin 1 g orally in a single dose 1, 5 OR
• Doxycycline 100 mg orally twice daily for 7 days 1, 6

Alternative Regimens:

• Erythromycin base 500 mg orally four times daily for 7 days
• Erythromycin ethylsuccinate 800 mg orally four times daily for 7 days
• Ofloxacin 300 mg orally twice daily for 7 days
• Levofloxacin 500 mg orally once daily for 7 days 1

For Neonatal Infections

Recommended Regimen for Ophthalmia Neonatorum and Pneumonia:

• Erythromycin base or ethylsuccinate 50 mg/kg/day orally divided into four doses daily for 14 days 1

Important note: Topical antibiotic therapy alone is inadequate for treatment of chlamydial infection and unnecessary when systemic treatment is administered 1

Screening Recommendations

• All sexually active women aged <25 years
• Older women with risk factors (new or multiple sex partners)
• All pregnant women
• Not currently recommended for routine screening in men 1

Prevention

• Consistent and correct use of barrier contraceptives
• Partner notification and treatment
• Regular screening of high-risk populations
• Treatment of infected pregnant women to prevent perinatal transmission

Clinical Pitfalls to Avoid

1. Missing asymptomatic infections: The majority of infections are asymptomatic, making screening crucial for detection.

2. Inadequate partner treatment: Failure to treat partners leads to reinfection.

3. Relying on topical treatment for neonatal infections: Systemic antibiotics are required.

4. Overlooking potential complications: Always consider the possibility of ascending infection and complications.

5. Failing to retest after treatment in high-risk individuals: Consider retesting to ensure cure and detect reinfection.

6. Neglecting to screen pregnant women: Screening is essential to prevent perinatal transmission.